Six workers have been killed since 1998 in the hundreds of mines that operate in Wisconsin.
The state has only one underground mine -- Maiden Rock in Pierce County -- and it produces silica sand, not coal like the underground mine in West Virginia, where 12 miners were killed.
State mine safety division specialist Richard Chier says that compared to other industries in man-hours worked, mining is very safe in Wisconsin.
Mineral resource specialist Bruce Brown of the Wisconsin Geological Survey says the state regulates under its mining laws, more than two-thousand stone quarries and gravel pits.
Federal records show that since 1997, Maiden Rock has received 27 citations following federal inspections and paid about $28,000 in penalties.
Because it's an underground operation, four federal inspections are done annually.